1. Technical Field
The present invention relates to a subminiature fuse.
2. Description of Prior Arts
In recent years, electronic appliances have become increasingly miniaturized and as a consequence, electric components constituting an electric circuit, for example, are also being considered for further miniaturization. Furthermore, in connection with withstand voltage, a high potential such as 200 V wiring is gradually becoming commonly accepted for household use and as a result miniature fuses which can be used in a range from a low voltage such as a few volts required for printed circuit boards to a high voltage exceeding AC 125 V are increasing in demand. Various sorts of miniature fuses have been developed in order to satisfy these requirements. As an example of miniature fuses which have been developed so far, there is available a type having the fuse wire completely embedded in resin to thereby easily attain miniaturization. However, a fuse of this sort suffers from drawbacks such that in the case of a relatively small overcurrent flowing therethrough due, for example, to failure of a transistor, Joule heat may be absorbed by the resin encircling the fuse wire resulting in a delay in the fusion time or the fuse may not melt until a sufficient number of elements are damaged to cause a flow of overcurrent high enough to melt the fuse. When a large current of a voltage exceeding AC 125 V is caused to flow due to short-circuiting or the like, since the fuse wire is entirely surrounded by resin, there is therefore nowhere room for metallic vapor generated by the melted, vaporized and expanded metallic component by the large current to be released. In consequence, the arcing time may be prolonged and the resin surrounding the fuse wire may be caused to shatter and scatter, thus causing potential hazard. In order to solve the problems as pointed out above, a miniature fuse has been developed wherein the area surrounding the fuse wire is filled with an arc-extinguishing material to thereby prevent the resin from being fractured by a large current. However, in the same manner as in the fuse as earlier mentioned, Joule heat may be absorbed by the arc-extinguishing material in the case of a small overcurrent and in this sense the problem that the fuse wire may not be melted away unless an excessively large current is caused to flow could not be entirely solved and the developed miniature current fuse as mentioned above was still not reliable.